1. Field of the Invention
The present invention relates to an electron emitter including a first electrode, a second electrode and an emitter section interposed between the first electrode and the second electrode. The emitter section is made of a dielectric material.
2. Description of the Related Art
In recent years, electron emitters having a cathode electrode and an anode electrode have been used in various applications such as field emission displays (FEDs) and backlight units. In an FED, a plurality of electron emitters are arranged in a two-dimensional array, and a plurality of fluorescent elements are positioned at predetermined intervals in association with the respective electron emitters.
Conventional electron emitters are disclosed in Japanese laid-open patent publication No. 1-311533, Japanese laid-open patent publication No. 7-147131, Japanese laid-open patent publication No. 2000-285801, Japanese patent publication No. 46-20944, and Japanese patent publication No. 44-26125, for example. All of these disclosed electron emitters are disadvantageous in that since no dielectric body is employed in the emitter section, a forming process or a micromachining process is required between facing electrodes, a high voltage needs to be applied between the electrodes to emit electrons, and a panel fabrication process is complex and entails a high panel fabrication cost.
It has been considered to make an emitter section of a dielectric material. Various theories about the emission of electrons from a dielectric material have been presented in the documents: Yasuoka and Ishii, “Pulsed electron source using a ferroelectric cathode”, J. Appl. Phys., Vol. 68, No. 5, p. 546-550 (1999), V. F. Puchkarev, G. A. Mesyats, “On the mechanism of emission from the ferroelectric ceramic cathode”, J. Appl. Phys., Vol. 78, No. 9, 1 Nov. 1995, p. 5633-5637, and H. Riege, “Electron emission ferroelectrics—a review”, Nucl. Instr. and Meth. A340, p. 80-89 (1994).
In the conventional electron emitters, electrons trapped on the surface of the dielectric material, at the interface between the dielectric material and the upper electrode, and in the dielectric material by the defect level are released (emitted) when polarization reversal occurs in the dielectric material. The number of the electrons emitted by the polarization reversal does not change substantially depending on the voltage level of the applied voltage pulse.
However, the electron emission is not performed stably, and the number of emitted electrons is merely tens of thousands. Therefore, conventional electron emitters are not suitable for practical use. Advantages of an electron emitter having an emitter section made of a dielectric material have not been achieved.